Historical Events in Fiber Optic Technology

When we talk about the history of fiber opitcs, we need to at least start from the year 1880. In fact, the use of light for communication has been a pre-historic invention by our ancestors. Leaving that pre-hisotric and the use of light signals in light-houses to direct ships, the history of modern fiber optics starts from 1880 when Alexander Graham Bell and his assistant Charles Sumner Tainter created a photophone.

The photophone developed by Bell and Tainter at the Volta laboratory in Washington D.C. That invention was a breakthrough and a guidance to many other inventors. That was a preliminary photophone, yet valued by the scientific community as one of the milestone in the development of Fiber optics as a separate branch of technology and a branch in physics and engineering in later years. The first photophone allowed transmission of sound on a beam of light. On June 3, 1880, Bell and his assistant conducted the first wireless telephone transmission between two buildings, some 213 meters apart. The medium for transmission was the atmosphere. Due to this reason, Bell’s photophone was not very useful practically.

Concerns over security and high transmission loss when transmitted through air diverted researchers to look in to another suitable medium for light. It leads them to focus to develop efficient trasmitter and receivers apart from the low loss physical medium. The Photophone’s first practical use came in military communication systems many decades later.

The Nobel prize winner Charles K. Kao and George Hockham postulated that the reason for high loss in optical fibers was due to the contaminations, which could be removed potentially. Their work at STC Laboratories (STL) at Harlow, England showed that the losses of 1000 dB/km in existing glass (compared to 5-10 dB/km in coaxial cable) could be removed lead to the invention of low loss optical fibers.

Thus the first optical fiber with significantly less attenuation was successfully developed in 1970 by Corning Glass Works.  The attenuation was low enough for communication purposes (about 20dB/km). At the same time GaAs semiconductor lasers were developed that were compact and therefore suitable for transmitting light through fiber optic cables for long distances.

The researches in the field of laser and optical fibers lead to the development and commercial deployment of fiber optic communication systems for the first time starting from 1975. The first fiber optic communication system was operated at a wavelength around 0.8 µm by using GaAs semiconductor lasers. This first generation fiber optic communication system was operated at a bit rate of 45 Mbps. The repater spacing was up to 10 km. In April 1977, General Telephone and Electronics transmitted the first live telephone traffic through optical fibers at a speed of 6 Mbit/s throughput in Long Beach, California.

There was no looking back for developments in the field of fiber optics. Optical fibers are now deployed directly to home to provide required bandwidth demanded by the end-users.

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Author: Prakash

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